This invention pertains to a packet communication system, a network-side apparatus to be used therein, and a time slot allocation control method wherein plural terminal-side apparatus are connected with a network-side apparatus sharing physical media, and the network-side apparatus allocates time slots dynamically according to the varying traffic of each terminal-side apparatus.
As a prospective system for realizing access network at a low cost, there is a media-shared type one-to-plural communication system wherein plural terminal-side apparatus are connected with one network-side apparatus sharing physical media. As an example of such media-shared type one-to-plural communication system, an ATM-PON (Asynchronous Transfer Mode-Passive Optical Network) system with 4 terminal-side apparatus is shown in FIG. 1. In the ATM-PON system, as shown in FIG. 1, the terminal-side apparatus 800xcx9c830 are connected with one network-side apparatus 840 via the optical branch/merger device 860. In such an ATM-PON system, so as to avoid collisions of data (henceforth described as cells) on the transmission line (henceforth described as shared transmission line) 870 between the optical branch/merger device and the network-side apparatus 840, shared by all the terminal-side apparatus connected to the network-side apparatus 840, each of the terminal-side apparatus 800xcx9c830 use time slots allocated by the network-side apparatus 840 to transmit cells to the network-side 840. If the network-side apparatus 840 allocates fixed time slots to each of the terminal-side apparatus 800xcx9c830, and one accommodates the Best Effort traffic having strong burst characteristics such as Internet service, the transmission capacity of the shared transmission line 870 may not be effectively utilized, because a certain amount of time slots are allocated fixedly in spite of the varying input traffic. Thus, in order to utilize the shared transmission line 870 effectively, the network-side apparatus 840 is required to change the time slot allocation dynamically according to the input state of the traffic to each of the terminal-side apparatus 800xcx9c830.
A prior art in which the network-side apparatus changes dynamically the time slot allocation to each of the terminal-side apparatus 800xcx9c830 as stated above, is described, for example, in JPAH10-242981, xe2x80x9cDynamic time slot allocation systemxe2x80x9d. With reference to FIG. 1, the time slot allocation control system described in the application above and a media shared type one-to-plural communication system to realize it will be described.
The terminal-side apparatus 800 comprises the Queue length (stored cell number, and hence forth described as Queue length) report function 802, which monitors the buffer 801 for storing input cells from each of terminals 880, 881 and the stored cell numbers in the buffer 801, and reports the Queue length information to the network-side apparatus 840, and to the output control function 803 which controls the output of cells in the buffer 801. Also the terminal-side apparatus 810, 820, and 830 are assumed to have a similar structure. And the network-side apparatus 840 is provided with the Queue length proportional time slot allocation control function 841 which calculates the time slot allocation for each of the terminal-side apparatus 800xcx9c830. The terminal-side apparatus 800xcx9c830 and the network-side apparatus 840 are connected by the separate transmission lines 850xcx9c853 connecting the terminal-side apparatus 800xcx9c830 with the optical branch/merger device 860, and by the shared transmission line 870 connecting the optical branch/merger device 860 with the network-side apparatus 840.
In such a structure, cells are transferred from the terminal-side apparatus 800xcx9c830 to the network-side apparatus 840 in the operation as will be described below. Cells input from the terminals 880, 881, are stored in the buffer 801, and then transferred to the network-side apparatus 840 by the output control function 803. The output control function 803 uses the time slots allocated by the Queue length proportional time slot allocation control function 841 of the network-side apparatus 840 to output cells to the network-side apparatus 840. The Queue length of the buffer 801 is also monitored by the Queue length report function 802, and the Queue length information is reported to the network-side apparatus 840 by the Queue length report function 802. Cells output from the terminal-side apparatus 800xcx9c830 and the Queue length information of the buffer 801 are input to the Queue length proportional time slot allocation control function 841 of the network-side apparatus 840 via the separate transmission lines 850xcx9c853, the optical branch/merger device 860, and the shared transmission line 870.
The Queue length proportional time slot allocation control function 841 of the network-side apparatus 840 allocates time slots to each of the terminal-side apparatus 800xcx9c830 according to the proportion based on the Queue length information of the buffer 801 reported from the Queue length report function 802. And the information about the allocated time slots is reported to each of the terminal-side apparatus 800xcx9c830 by the control signal 890.
As an example, in case Queue lengths of the buffer for each of the terminal-side apparatus are 20, 50, 40, and 10 respectively, and the total time slots allocated to each of the terminal-side apparatus 800xcx9c830 is 60, time slot allocation will be described with reference to FIG. 2. In FIG. 2, Queue lengths and allocated time slot numbers in the buffer 801 are shown for each of the terminal-side apparatus 800xcx9c830. In this case, the Queue length proportional time slot allocation control circuit 841 allocates the total time slots of 60 to each of the terminal-side apparatus 800xcx9c830, according to the Queue length ratio 20:50:40:10 in the buffer 801 for each of the terminal-side apparatus 800xcx9c830. Thus the time slot numbers allocated to each of the terminal-side apparatus 800xcx9c830, turn out to be 10, 25, 20, 5.
As described as above, in a conventional time slot allocation control system where the time slot is allocated in proportion to the Queue length of each of the terminal-side apparatus, time slot allocation is based on the input state of the traffic to each of the terminal-side apparatus. Thus, transmission capacity of the shared transmission line 870 is effectively utilized.
In a system of the prior-art, when the time slot allocation is changed, the total time slots are allocated to each terminal-side apparatus, according to the proportion of the Queue length of each terminal-side apparatus. Thus, time slots are allocated even to terminal-side apparatus having buffer of short Queue length, and sufficient time slots may not be allocated to terminal-side apparatus having buffer of long Queue length. As a result, there is a problem where buffer capacity necessary may increase so as to satisfy a certain cell loss rate, as the Queue length of buffer having long Queue length increases.
In the conventional allocation methods according to the ratio of Queue lengths, since the ratio of Queue lengths is that of values of the Queue length minus the time slot number allocated, the variance of Queue lengths among each of the terminal-side apparatus is large even in a steady state. The buffer capacity necessary is determined by the longest Queue length of the buffer of all the terminal-side apparatus, and the larger the variance of Queue lengths among terminal-side apparatus, the larger the buffer capacity necessary.
It is an object of the invention to provide a time slot allocation control method wherein the buffer capacity necessary for the buffer of each terminal-side apparatus may be reduced in a dynamic time slot allocation control, and provide a one-to-plural media shared type communication system to realize it.
According to the first feature of the invention, a packet communication system, wherein plural terminal-side apparatus and a network-side apparatus are connected, sharing physical media, said network-side apparatus allocating time slots to at least one of said terminal-side apparatus, and said terminal-side apparatus transferring packets to the physical media by using said time slots, each of said terminal-side apparatus comprises:
a buffer means for storing packets input from plural terminals connected and a packet number report means which monitors the number of packets presently stored in said buffer means and reports said packet number information to said network-side apparatus, and said network-side apparatus comprising a time slot allocation control means for allocating time slots to each said terminal-side apparatus on the basis of stored packet information from the packet number report means of said terminal devices, and said time slot allocation control means allocates time slots by allocating time slots so that the stored packet number minus the number of time slots allocated to each may approach a specified value.
According to the second feature of the invention, a packet communication system, wherein plural terminal-side apparatus and a network-side apparatus are connected, sharing physical media, said network-side apparatus allocating time slots to at least one said terminal-side apparatus, and said terminal-side apparatus transferring packets to the physical media by using said time slots, each of said terminal-side apparatus comprises:
a buffer means for storing packets input from plural terminals connected and a packet number report means which monitors the number of packets presently stored in said buffer means and reports said packet number information to said network-side apparatus, and said network-side apparatus comprising a time slot allocation control means for allocating time slots to each said terminal-side apparatus on the basis of stored packet information from the packet number report means of said terminal devices, and said time slot allocation control means allocates time slots by allocating time slots so that the variance of the stored packet number minus the number of time slots allocated to each may be minimized.
According to the third feature of the invention, a packet communication system, wherein plural terminal-side apparatus and a network-side apparatus are connected, sharing physical media, said network-side apparatus allocating time slots to at least one of said terminal-side apparatus, and said terminal-side apparatus transferring packets to the physical media by using said time slots, each of said terminal-side apparatus comprises:
a buffer means for storing packets input from plural terminals connected and a packet number report means which monitors the number of packets presently stored in said buffer means and reports said packet number information to said network-side apparatus, and said network-side apparatus comprising a time slot allocation control means for allocating time slots to each said terminal-side apparatus on the basis of stored packet information from the packet number report means of said terminal device, and said time slot allocation control means divides the total time slots allocated for said terminal-side apparatus into time slot groups, allocating time slots so that in each said time slot group, the stored packet number in said terminal-side apparatus minus the number of time slots allocated to each may approach a specified value, adding each said allocated time slot in each said terminal-side apparatus to determine the allocated time slots in said terminal-side apparatus.
According to the fourth feature of the invention, a packet communication system, wherein plural terminal-side apparatus and a network-side apparatus are connected, sharing physical media, said network-side apparatus allocating time slots to at least one said terminal-side apparatus, and said terminal-side apparatus transferring packets to the physical media by using said time slots, each of said terminal-side apparatus comprises:
a buffer means for storing packets input from plural terminals connected and a packet number report means which monitors the number of packets presently stored in said buffer means and reports said packet number information to said network-side apparatus, and said network-side apparatus comprising a time slot allocation control means for allocating time slots to each said terminal-side apparatus on the basis of stored packet information from the packet number report means of said terminal devices, and said time slot allocation control means divides the total time slots allocated for said terminal-side apparatus into time slot groups, allocating time slots so that in each said time slot group, the variance of the stored packet number in said terminal-side apparatus minus the number of time slots allocated to each may be minimized, adding each of said allocated time slots in each said terminal-side apparatus to determine the allocated time slots in said terminal-side apparatus.
According to the fifth feature of the invention, a packet communication system, wherein plural terminal-side apparatus and a network-side apparatus are connected, sharing physical media, said network-side apparatus allocating time slots to at least one said terminal-side apparatus, and said terminal-side apparatus transferring packets to the physical media by using said time slots, each of said terminal-side apparatus comprises:
a buffer means for storing packets input from plural terminals connected and a packet number report means which monitors the number of packets presently stored in said buffer means and reports said packet number information to said network-side apparatus, and said network-side apparatus comprising a time slot allocation control means for allocating time slots to each said terminal-side apparatus on the basis of stored packet information from the packet number report means of said terminal device, and said time slot allocation control means divides the total time slots allocated to said terminal-side apparatus into plural slot groups, allocates time slots so that in at least one of said time slot groups, the stored packet numbers in said terminal-side apparatus minus the time slot numbers allocated may approach a specified value, and in the other time slot groups among said time slot groups, the variance of the stored packet numbers in said terminal-side apparatus minus the time slot numbers allocated may be minimized, adding each said allocated time slot in each said terminal-side apparatus to determine the allocated time slots in said terminal-side apparatus.
According to the sixth feature of the invention, a packet communication system defined in claim 1, wherein in said time slot allocation control means, time slots are allocated in the descending order of stored packet numbers in the terminal-side apparatus when time slots are allocated.
According to the seventh feature of the invention, a packet communication system defined in claim 1, wherein in said time slot allocation control means, terminal-side apparatus for time slot allocation are limited to part of them when time slots are allocated.
According to the eighth feature of the invention, a packet communication system defined in claim 1, wherein when said time slot allocation control means are limited to part of terminal-side apparatus for allocation, terminal-side apparatus which store packets more than a predetermined threshold value are chosen.
According to the ninth feature of the invention, a packet communication system defined in claims 1, wherein when said time slot allocation control means are limited to part of terminal-side apparatus for allocation, a predetermined number of terminal-side apparatus are chosen in the descending order of stored packet numbers.
According to the tenth feature of the invention, a packet communication system defined in claims 1, wherein when said time slot allocation control means are limited to part of terminal-side apparatus for allocation, a predetermined number of terminal-side apparatus are chosen in the descending order of stored packet numbers among those which store packets more than a predetermined threshold value.
According to the eleventh feature of the invention, a packet communication system defined in claim 1, wherein when said time slot allocation control means are limited to part of terminal-side apparatus for allocation, among a predetermined number of terminal-side apparatus in the descending order of stored packet number, terminal-side apparatus with packets more than a predetermined threshold value are chosen
According to the twelfth feature of the invention, a packet communication system defined in claim 1, wherein said packets are cells used in the asynchronous transfer mode.
According to the thirteenth feature of the invention, a network-side apparatus wherein it is provided with a stored packet number management table which manages the stored packet number information reported from plural terminal-side apparatus and updates the stored packet number information under management when new packet number information is reported from each said terminal-side apparatus, a circuit for determining terminal-side apparatus for allocation, which gets the stored packet information of each said terminal device with reference to said stored packet number management table when timing arrives for changing time slot allocation and limits terminal-side apparatus for allocation on the basis of the acquired stored packet number information, and a time slot allocation control circuit which when the information of the terminal-side apparatus for allocation is received from said circuit for determining terminal-side apparatus for allocation, gets the stored packet number information of the terminal-side apparatus for allocation with reference to said stored packet number management table, allocates time slots to the terminal-side apparatus for allocation based on the acquired stored packet number information, and reports the allocated time slot information to the terminal-side apparatus.
According to the fourteenth feature of the invention, a network-side apparatus defined in claim 13, wherein the terminal-side apparatus stored with packets more than a predetermined threshold value are chosen, when said circuit for determining terminal-side apparatus for allocation limits terminal-side apparatus for allocation to part of terminal-side apparatus.
According to the fifteenth feature of the invention, a network-side apparatus defined in claim 13, wherein a predetermined number of terminal-side apparatus are chosen in descending order of numbers of stored packets, when said circuit for determining terminal-side apparatus for allocation limits terminal-side apparatus for allocation to part of terminal-side apparatus. 16.A network-side apparatus defined in claim 13, wherein among the terminal-side apparatus stored with packets more than a predetermined threshold value, a predetermined number of terminal-side apparatus are chosen in the descending order of stored packet numbers, when said circuit for determining terminal-side apparatus for allocation limits terminal-side apparatus for allocation to part of terminal-side apparatus.
According to the seventeenth feature of the invention, a network-side apparatus defined in claim 13, characterized in that among a predetermined number of the terminal-side apparatus in the descending order of stored packet numbers, terminal-side apparatus stored with more than a predetermined threshold value are chosen when said circuit for determining terminal-side apparatus for allocation limits terminal-side apparatus for allocation to part of terminal-side apparatus.
According to the eighteenth feature of the invention, a network-side apparatus defined in claim 13, wherein said time slot allocation control circuit allocates time slots so that values of the stored packet numbers of said terminal-side apparatus minus the time slot numbers allocated may approach a specified value.
According to the nineteenth feature of the invention, a network-side apparatus defined in claim 13, wherein said time slot allocation control circuit allocates time slots so that the variance of the stored packet numbers of said terminal-side apparatus minus the time slot numbers allocated may be minimized.
According to the twentieth feature of the invention, a network-side apparatus defined in claim 13, wherein said time slot allocation control circuit divides the total time slots allocated to said terminal-side apparatus into plural time slot groups and allocates time slots so that in each of said time slot group the stored packet numbers of said terminal-side apparatus minus the numbers of time slots allocated may approach a specified value, determining the allocated time slots for said terminal-side apparatus by adding each said time slot allocated to each said terminal device.
According to the twenty-first feature of the invention, a network-side apparatus defined in claim 13, wherein said time slot allocation control circuit divides the total time slots allocated to said terminal-side apparatus into plural time slot groups and allocates time slots so that in each of said time slot group the variance of stored packet numbers of said terminal-side apparatus minus the numbers of time slots allocated may be minimized, determining the allocated time slots for said terminal-side apparatus by adding each said time slot allocated to each said terminal device.
According to the twenty-second feature of the invention, a network-side apparatus defined in claim 13, wherein said time slot allocation control circuit divides the total time slots allocated to said terminal-side apparatus into plural time slot groups, and allocates time slots so that in at least one group of said time slot groups, the stored packet numbers of said terminal-side apparatus minus the numbers of time slots allocated may approach a specified value, and in the other time slot groups of said time slot groups, the variance of stored packet numbers of said terminal-side apparatus minus the numbers of time slots allocated may be minimized, determining the allocated time slots for said terminal-side apparatus by adding each of said time slots allocated to each of said terminal devices.
According to the twenty-third feature of the invention, a network-side apparatus defined in claim 18, wherein said time slot allocation control circuit allocates time slots to terminal-side apparatus in the descending order of stored packet numbers.
According to the twenty-fourth feature of the invention, a network-side apparatus defined in claim 13, further comprises:
a time slot group deterministic circuit which divides the total time slots allocated to said terminal-side apparatus into plural time slot groups to manage them, and an addition circuit which inputs the results of time slot allocation from plural number of said time slot allocation control circuits, adds each allocation result, reporting the added results to each said terminal-side apparatus.
According to the twenty-fifth feature of the invention, a network-side apparatus defined in claim 13, wherein said packets are cells used in the asynchronous transfer mode.
According to the twenty-sixth feature of the invention, a time slot allocation control method wherein plural terminal-side apparatus and network-side apparatus are connected sharing physical media and said network-side apparatus determines the time slot numbers allocated to said terminal-side apparatus, said terminal-side apparatus seek the stored packet numbers in terminal-side apparatus, and said network-side apparatus seeks the time slot numbers for allocation, and time slots are so allocated that said stored packet number minus the time slot number allocated to each may approach a specified value.
According to the twenty-seventh feature of the invention, a time slot allocation control method wherein plural terminal-side apparatus and a network-side apparatus are connected, sharing physical media and said network-side apparatus determines the time slot numbers allocated to said terminal-side apparatus, and said terminal-side apparatus seek the stored packet numbers in the terminal-side apparatus, and said network-side apparatus seeks the time slot numbers, and time slots are so allocated that the variance of said stored packet numbers minus the time slot numbers allocated to each may be minimized.
According to the twenty-eighth feature of the invention, a time slot allocation control method wherein plural terminal-side apparatus and network-side apparatus are connected, sharing physical media, said network-side apparatus determining the time slot numbers allocated to said terminal-side apparatus, said terminal-side apparatus seek the stored packet numbers of terminal-side apparatus, and said network-side apparatus seeks the time slot numbers, and the total time slots are divided into plural time slot groups, and in each said time slot group, time slots are so allocated that the stored packet number of said terminal-side apparatus minus the time slot number allocated to each may approach a specified value, and the allocated time slots for said terminal-side apparatus are determined by adding each said time slot allocated to each said terminal device.
According to the twenty-ninth feature of the invention, a time slot allocation control method wherein plural terminal-side apparatus and network-side apparatus are connected, sharing physical media, said network-side apparatus determining the time slot number allocated to said terminal-side apparatus, said terminal-side apparatus seek the stored packet numbers of terminal-side apparatus, and said network-side apparatus seeks the time slot numbers, and the total time slots are divided into plural time slot groups, and in each said time slot group, time slots are so allocated that the variance of the stored packet numbers of said terminal-side apparatus minus the time slot numbers allocated to each may be minimized, and the allocated time slots for said terminal-side apparatus are determined by adding each said time slot allocated to each said terminal device.
According to the thirtieth feature of the invention, a time slot allocation control method wherein plural terminal-side apparatus and network-side apparatus are connected, sharing physical media, said network-side apparatus determining the time slot number allocated to said terminal-side apparatus, said terminal-side apparatus seek the stored packet numbers of terminal-side apparatus, and said network-side apparatus seeks the time slot numbers, and the total time slots are divided into plural time slot groups, and in at least one of said time slot groups, time slots are so allocated that stored packet number of said terminal-side apparatus minus the time slot number allocated to each may approach a specified value, and in the other time slot groups of said time slot groups, time slots are so allocated that the variance of stored packet numbers of said terminal-side apparatus minus the time slot numbers allocated to each may be minimized, and the allocated time slots for said terminal-side apparatus are determined by adding each said time slot allocated to each said terminal device.
According to the thirty-first feature of the invention, a time slot allocation control method defined in claim 26, wherein time slots are allocated in descending order of number of stored packets in the terminal-side apparatus.
According to the thirty-second feature of the invention, a time slot allocation control method defined in claim 26, wherein said packet allocation is limited to the terminal-side apparatus storing packets more than a preset threshold value.
According to the thirty-third feature of the invention, a time slot allocation control method defined in claim 26, wherein said packet allocation is limited to the terminal-side apparatus of a predetermined number in the descending order of stored packet numbers.
According to the thirty-fourth feature of the invention, a time slot allocation control method defined in claim 26, wherein among the terminal-side apparatus storing packets more than a predetermined threshold value, terminal devices for said packet allocation are limited to those of a predetermined number in the descending order of stored packet numbers.
According to the thirty fifth feature of the invention, a time slot allocation control method defined in claim 26, wherein among the terminal-side apparatus of a predetermined number in the descending order of stored packet number, terminal-side apparatus for said packet allocation are limited to those storing packets more than a predetermined threshold value.
According to the thirty-sixth feature of the invention, a time slot allocation control method defined in claim 26, wherein those said packets are cells used in the asynchronous transfer mode.